By Katherine Peng
From humans, to wookies, to Jar Jar Binks. With over 20 million species in the Star Wars galaxy, one can assume that not even this fictional universe is exempt from the laws of evolution. A conversation on how diverse environments pushed them to look so strange (or like cute little ewoks!) through rare mutations would be a discussion of the “hard inheritance” of DNA sequences, but what about soft inheritance? Can the surrounding environment in one lifespan change DNA in ways that can be passed on to offspring?
You’re shaking your head thinking DUH..NO, as thoughts jump back to the image of that giraffe in your biology 101 textbook. Remember that a once accepted theory of evolution proposed by Jean-Baptiste Lamarck suggested that acquired traits were inherited (e.g. a giraffe constantly stretching it’s neck to reach tall trees will give birth to giraffes with longer necks)? We now know that this theory is preposterous. What if Yoda lost his favorite toe in battle and decided to procreate? Would all future Yodas be afflicted with the curse of having only 5 toes?
BUT WAIT. Lamarck might have been onto something after all! Molecular biology has found that environmental factors CAN affect DNA without altering the sequence, and that these changes can be passed on to future generations (though not often beneficially). Welcome to the field of epigenetics!
In all eukaryotic cells in ours and the Star Wars galaxy, DNA is packaged around histone proteins. This DNA can be methylated and/or the histones can be modified to silent gene expression. People nowadays are becoming increasingly interested in how environmental factors produce these epigenetic changes and affect disease patterns.Genome-wide epigenetic studies are more commonly done on identical twins, where differences between individuals must be environmental. While Luke and Leia Skywalker are fraternal twins, sharing ~50% of their genes as would regular siblings, they were separated at birth to be raised in different environments. So, let’s take a look at how they become more different than their genetics would have us believe.
In 2004, researchers from McGill University discovered that early nurturing from rat mothers remove epigenetic repression of the glucocorticoid receptor gene in rat pups. Consequently, rats that were not well nurtured became more sensitive to stress as adults.
Though childhood scenes of Luke and Leia are basically nonexistant, we do know that Leia was adopted into a very loving royal family who could not have children of their own. Luke was adopted by his step-uncle and step-uncle’s wife. His step-uncle did not approve of his adventurous tendencies, which created tension.
VERDICT: Though both twins are at risk of higher stress responses due to Amidala’s likely depression during pregnancy, hints of a less nurturing environment suggest that Luke may be more sensitive to stress as an adult than Leia.
The Swedes are on a role in this category. A recent Swedish study shows that 20 minutes of exercise can reverse DNA methylation of genes in muscle that show lowered expression in type 2 diabetes. Another shows that 6 months of exercise changed the methylation pattern of genes in fat cells implicated in the risk of developing obesity or diabetes.
While Luke is working the moisture farm in Tattoine and having adventures, Leia is a palace princess in Alderaan.
VERDICT: While it seems that both Luke and Leia are fit later on, Luke appeared more active as a child and may be at a lower risk for type 2 diabetes. Sorry Leia.
Bioactive food components (in tea, soybean, etc.) might beneficially reduce DNA hypermethylation of cancer associated genes. On the flip side, folate found in fresh produce is required for DNA methylation, and its deficiency in pregnant moms may cause disease or cancer in children. You are also what your father eats. A mouse study showed that a paternal low-protein diet created upregulation of lipid biosynthesis in offspring.
Unfortunately, there’s no real information out there on the diet of the Skywalkers so…
So what have we learned here today? Leia needs to ramp up her training, and Luke should control that anxiety before he becomes like his father. But really, epigenetic changes in twins aren’t too different until later in life so I guess it’s all speculation until Disney releases the first installment of the sequel trilogy.